1. Field of Use
The process of this invention relates to the preparation of a 5,6,7,8-tetrahydro-1-alkenyl-9,10-anthraquinone by oxidizing the adduct of a triene and tetrahydronaphthaquinone in the presence of molecular oxygen, a strong organic base and optionally a solvent.
2. Prior Art
The use of alkylanthraquinones and/or their tetrahydro derivatives as working intermediates in cyclic reduction-oxidation processes for producing hydrogen peroxide is well known. In such processes, commonly referred to as anthraquinone processes, the working intermediate or mixture of two or more thereof is dissolved in a suitable water immiscible solvent or mixture of solvents and the solution is alternately reduced and oxidized. In the reduction stage, the working intermediate is hydrogenated in the presence of a suitable catalyst to reduce it to its anthrahydroquinone form. In the subsequent oxidation stage, the intermediate is reoxidized with molecular oxygen, e.g., in the form of air, to reform the anthraquinone and simultaneously produce hydrogen peroxide. The hydrogen peroxide is then removed from the working solution, generally by extraction with water, and the residual anthraquinone working solution is recycled to the reduction stage for a repetition of the cycle.
Canadian Pat. No. 614,296 issued to Ferri on Feb. 7, 1961, and the following U.S. patents (issue dates in parentheses) are representative of the many issued patents relating to anthraquinone processes for producing hydrogen peroxide: Reidl et al., U.S. Pat. Nos. 2,158,525 (5/16/39) and 2,215,883 (9/24/40); Dawsey et al., U.S. Pat. No. 2,537,655 (1/9/51); Sprauer, U.S. Pat. No. 2,657,980 (11/3/53); Harris et al., U.S. Pat. No. 2,668,753 (2/9/54) and Hinegardner, U.S. Pat. No. 2,689,169 (9/14/54) and Darbee et al., U.S. Pat. No. 3,062,622 (11/6/62); Hiratsuka et al., U.S. Pat. No. 3,038,786 (6/12/62); Dawsey, U.S. Pat. No. 3,041,143 (6/26/62); Kabisch, U.S. Pat. No. 3,328,128 (6/27/67); Kabisch et al., U.S. Pat. No. 3,488,150 (1/6/70) and Logan et al., U.S. Pat. No. 3,493,343 (2/3/70).
As is recognized in such issued patents, it is important in commercial operations that the working solution employed have a high hydrogen peroxide synthesis capacity per cycle and that the hydrogen peroxide solution obtained in the extraction step be relatively concentrated. The concentration of the hydrogen peroxide is determined largely by the solubility of the working intermediate employed, particularly in its anthrahydroquinone form. Certain tetrahydro-1-alkyl-anthraquinones which are disclosed in U.S. Pat. No. 3,888,890 and which exhibit outstanding solubilities in working solvents of the type commonly used are particularly well suited for use in cyclic anthraquinone processes for producing peroxide. However, these tetrahydroanthraquinones are prepared by the catalytic reduction of the parent anthraquinone and significant anthraquinone losses can occur in this step.